Jul 20, 2020

Trigger crops’ own immune response in fight against disease

{Sponsored} Forcing crops to trigger their natural resistance mechanism can give growers of crops such as tomatoes and cucurbits a critical edge while tackling difficult fungal diseases such as downy mildew, Pythium and Phytophthora spp., says crop nutrition specialist OMEX® Agrifluids.

Known as ‘systemic acquired resistance’ (SAR), the protective mechanism is analogous to the human immune system. When a fungal spore, virus or insect breaches the plant’s physical defenses, it responds by releasing distinctive ‘pathogenesis-related’ (PR) proteins that can help the plant overcome the invader — or at least minimize its damaging effects.

“There’s still a lot of research being undertaken in universities and other institutions to better understand the response, the trigger mechanism and the receptors within the plant,” says Dean Konieczka, an agronomist with OMEX.

“But we do know that these receptors can be triggered by other naturally occurring compounds, in the absence of any immediate disease threat. With careful integration of these products into a crop management program, growers can exploit the PR proteins to bolster the plants’ natural defenses – much like we use vaccines ourselves.”

Although the mechanism isn’t strong enough to confer absolute disease resistance on a crop, the systemic influence – the PR proteins circulate throughout the plant – often has enough preventative effect to draw out the plant’s ability to withstand infection until the next stage of the fungicide program.

OMEX® has been working with a pair of compounds, monopotassium phosphate and monopotassium phosphite, in an attempt to harness the PR effect within a suitable product for use by growers.

“The phosphite element triggers SAR,” explains Dean. “When the plant absorbs phosphite through the leaf, it’s immediately translocated to the root system and processed into usable phosphate. Through this process the ‘immune’ response is triggered.”

Significantly, Dean notes, each of these two compounds also exhibits a fungicidal action. “That’s allowed us to secure national registration as a fungicide,” Dean points out, “without any restrictions at state level.

“Products containing the more common ammonium phosphite are often lumbered with label use restrictions,” he adds, “while other monopotassium phosphate products are often formulated with other constituents that either reduce tank-mix options or invite additional restrictions at state-level.”

Marketed as PhorcePhite, the OMEX® co-formulation has been embraced by growers who need a product with effective fungicidal qualities, while offering a zero-day harvest interval (HI) and no worker restrictions after the spray dries.

“This has proved a real benefit for growers with hi-tunnel greenhouses,” acknowledges Dean. “Very few disease suppressant products are approved for use in these structures and there’s little mechanization possible within a tunnel, necessitating hand harvesting.

“PhorcePhite gives growers an opportunity to keep crops protected ‘through the gap’ within a protective schedule, without incurring entry restrictions. For crops such as tomatoes and strawberries, where harvest is an ongoing process conducted by hand, this absence of restrictions removes a major headache for growers.”

A further benefit, Dean adds, is the nutritional value of the co-formulation. “Young crops coming out of the greenhouse, or being transplanted, often need a nutritional boost to help them through this stressful period. With no ammonium in the formulation, PhorcePhite isn’t ‘hot’ when used under these circumstances.”

Learn more at www.omexusa.com.

The product names and brands referenced here are registered and trademarks of OMEX® Agrifluids, Inc.

© OMEX® Agrifluids, Inc. 2020.